Some of the most endearingly personal updates can be seen in Pont Reading's four murals, created by artist Matthew Austin, who moved into the house for several weeks while doing the work. He painted lush landscapes filled with plants, vines, birds, and animals, but the true masterpiece is in Lucas's nursery, where he created a fantasy land with everything from robots to chimps and from birds to clouds—anything that might inspire stories or pay homage to existing ones. Special care was taken, too, to portray courageous kid moments, like a child in a boat surrounded by lightning ... who is smiling and covering his ears. The mural is done in the style of a child's drawing, which Austin found surprisingly difficult after years of mastering classical painting techniques: "It's hard to become innocent with your hand again—artistically, you have to unlearn everything you've been taught." To get the truest kidlike results, Austin ended up drawing a lot of the animal figures with his left hand and his feet. "It was the most fun mural I've ever done," he says. "I was in such a different territory."

The kitchen served up another opportunity for mixing the olde with the new. This airy space was originally three cramped rooms with very little natural light, and an enclosed staircase that descended into it divided the space unnecessarily. Yague and DeWitt opened things up by exposing the staircase; now an integrated element, it connects the kitchen to the floor above more sensibly. They then removed most of the internal walls, creating one open area, and installed new mullion windows all around that offer a view of the garden. The Restoration Glass used in the windows make them seem as if they have always been there.

Now the generously sized kitchen blends original and new cabinetry, as well as a large custom-built island, all treated with a casein-paint finish, so everything looks of the same period. The room has the house's only television, as well as a sofa where you'll often find a grandparent, a guest, or one of the family's two vizslas. "I wanted us all to be together when we're cooking," says DeWitt, who often puts Lucas's seat on the marble countertops. "I didn't want someone to be alone in the kitchen and someone else to be watching TV in another part of the house." As is the case with many family rooms across the country, this space—wide, welcoming, and flooded with natural light—is the heart of the house.

With the relentless demands of a growing baby as well as another infant due this summer (again by surrogate), the couple haven't had a lot of time to finesse every corner of the house. But that doesn't bother either of them—they want the rooms to feel like they have evolved over time, not like they've been thrown together all at once. "Pont Reading may be historic," observes DeWitt, "but it's also a place that has grown organically over all these years." Here's to aging gracefully.